Conventional electronic keyboards usually comprise a base which supports a matrix board that defines the keyboard's key positions. Each position includes a pair of switch contacts, a spring-biased plunger and a key cap for depressing the plunger which thereupon allows the spring contacts to come together. This completes an electrical circuit to initiate a selected function, e.g. the printing of a character associated with the depressed key. Thus, the manufacture of the keyboard as a whole requires the hand assembly of a large number of small parts which is time consuming and expensive. Also, there is ample opportunity for misassembly of those parts. Furthermore, electrical connections have to be made between the switch contacts at the different key positions and a printed circuit board, further adding to the time required to assemble keyboards of this general type.
There do exist membrane keyboards or touch pads which are used in some calculators and in the control panels for some appliances such as radar ovens. See, for example, U.S. Pat. Nos. 3,773,998; 3,978,297; 3,982,081 and 4,028,509. However, those prior apparatus are not entirely suitable as full keyboards for use with a computer, printer, display terminal, or the like. First of all, the "keys" on most of those pads do not move to any appreciable extent. Therefore, they do not provide any feedback to the operator which is desirable if the operator is to "type" accurately at a reasonably high rate of speed. Also the switches incorporated into those prior membrane keyboards at the different key positions are generally not reliable or durable enough for this application and the electrical signals they initiate are not always consistent and uniform.
Those prior pads which do have movable keys tend to require relatively complicated spring structures associated with the keys. Often the keys do not have the right feel as far as the operator is concerned and rapid operator fatigue results.
Also in the usual full keyboard, the key positions are arranged in columns and rows with the rows further away from the front of the keyboard being located at progressively higher levels or elevations like the keys of a conventional typewriter. It has been the convention to regard the second key row or level above the space bar as the so-called home row over which the fingertips are usually returned after reaching for keys in the other rows.
To enable the operator's fingertips to properly contact the keys in the different rows, the tops of the key caps in the different rows have different shapes or profiles. For example, in a typical keyboard, the tops of the key caps in the home row may be more or less horizontal. On the other hand, the tops of the key caps in the topmost row are angled downwardly, the angle being such as to more or less match the angle of the operator's fingertips when he reaches for those keys. Conversely, the key caps in the lowest or front row of the keyboard may be angled upwardly to account for the fact that the operator's fingers have to reach back and down in order to properly depress those keys. This means that several differently sculptured key caps must be manufactured for each keyboard. Not only are there attendant die costs, but also these caps must be separately inventoried and they must be installed in the correct rows of the keyboard, adding to the overall cost of keyboards of this general type.
Also, because the keys are different as aforesaid, each key is dedicated to a particular row or rows of the keyboard. Therefore, it is not possible to change the format of the keyboard by rearranging the keys, e.g. from a telephone format to a calculator format.
Conventional electronic keyboards have other drawbacks as well. Some are excessively noisy in that they emit a clacking sound when the operator rapidly depresses the keys one after the other in the manner of a competent typist. Some prior keyboards of this type do not satisfy the height standard recently agreed upon by European countries which requires that the height of the keys in the home row be no more than 30 mm. from the surface upon which the keyboard rests.